Pumps traditionally fall into two major groups: rotor-dynamic pumps and positive displacement pumps. Their names describe the method used by the pump to move fluid. Rotor-dynamic pumps are based on bladed impellers which rotate within the fluid to impart a tangential acceleration to the fluid and a consequential increase in the energy of the fluid. The purpose of rotor-dynamic pumps is to convert this kinetic energy into pressure energy in the associated piping system. A positive displacement pump causes a liquid or gas to move by trapping a fixed amount of fluid or gas and then forcing (displacing) that trapped volume into the discharge pipe. In both these types of pumps the fluid motion can be considered as moving in two dimensions along a plane.
No matter what type of pump is used, they all have one common design feature: the mobile part (rotor or turbine) is located in a rugged sealed case (stator). This design primarily increases the weight and size of the pump. The pump also requires many different parts such as bushings, gears seals etc. Given that a pump with high productivity Q (liter/min) requires a very high rotation speed (RPM) these additional mechanical parts result in a variety of different negative effects in terms of vibration, friction losses, noise, large power consumption and pulsation of the fluid stream which reduce the reliability of the pump.
A volumetric rotor machine has been developed for use in hydro mechanical engineering which does not require a waterproof case because the areas of high and low pressure are formed within the rotating units The rotor machine is formed of six rotors fixed in an axial direction on motionless, mutually perpendicular axes. Each rotor has the form of a truncated cone with two symmetric spiral recesses provided on the lateral surface of the rotor which acts to co-operate with the adjacent rotors. Channels of low pressure are formed in the mechanism by the periodic creation of a working chamber from the greater end faces of each of the rotors and channels of high pressure, by creating a working chamber from the small end faces of each of the rotors wherein the central part of the machine and the respective end faces form a cavity of high pressure and in one or more axes of the rotors, axial chambers are created. The mechanism is operated by being submerged in liquid and the surrounding liquid enters the mechanism from all sides in contrast to conventional pumps which as a rule, have a single inlet or suction port.
This volumetric machine was invented by A. V. Vagin in 1972 and was registered in the State Register of Inventions of the U.S.S.R. on Jan. 14 1975, as Invention Certificate 470190, now published as SU470190. As the original document is in Russian, we provide a translation of the description herein.
A general view of the volumetric rotor machine is shown in FIG. 1 with a view of one rotor shown in FIG. 2. Sections of a rotor are shown in FIGS. 3 to 6. Planar sections of the device where the plane passes through the axes of the rotors on angle φ equals 0°, 45°, 90° and 135° respectively, are shown in FIGS. 7 to 10.
The volumetric rotor machine contains six identical rotors, 1-6 each having the form of a truncated cone with two spiral recesses formed on the lateral surface. The recesses are formed such that their minimums lie coaxially with a conic rotor surface with an angle u1 at the top whereu1=arccos√⅔=35° 15′  (1)and the edges lie coaxially with a conic rotor surface with an angle u2 at the top, whereu2=arccos√⅓=54° 15′  (2)wherein the tops of both conic surfaces coincide with the top of a rotor. The lateral surface of a rotor in a spherical system of coordinates (r, u, φ) is described by the equations:u=arccos(t/√3)andφ=arcsin[(t2+t−2)/√2(3−t2)]+φ0(r)with 1≦t≦√2  (3)where φ0(r) is any monotonous function defining a view of spiral deepening and edges on a lateral surface of a rotor.
In the equations (3) the dependence φ(u) is essential at r=constant and for the function φ(r) at u=constant, monotony is important only. In other words, the form of section of a rotor by spherical surface with the centre in its top is the key factor and a twisting of a rotor in a spiral around its axis at transition from one horizontal section to another, defined by the additive φ0(r), should only be monotonous. The form of the face surfaces of the rotors is not essential.
Plane CC is the main axial plane of a rotor. Mutually perpendicular axes 7 of rotors are crossed at one point. The tops of all six rotors lie on a point of crossing of the semi-axes. Mutual orientation of rotors means that axial planes of rotors 1 and 2 pass through axes of rotors 3 and 4, the main axial planes of rotors 3 and 4 pass through axes of rotors 5 and 6 and the main axial planes of rotors 5 and 6 pass through axes of rotors 1 and 2.
Spiral rotors on lateral surfaces of rotors adjoin on the length to deepening on lateral surfaces of the next rotors so that periodic creation of working chambers inside the device form a cavity of high pressure 8 and in one or several axes of rotors, channels of high pressure the through channels of the working medium are executed and connected with the cavity 8 and the exhaust 9.
Channels of low pressure 10 are formed by periodic disclosing of working chambers from the side of the greater end faces of rotors.
The device possesses one internal rotary degree of freedom—turn of one of the rotors around the axis on any angle necessarily entails turn of the other rotors around of the axes on the same angle. At turn of rotors around the axes, the chamber inside the device remains closed and its volume periodically changes.
In an initial position, such as that shown in FIG. 7, the section of rotors 1 and 2 coincides with section A-A of a rotor on FIG. 3 and rotors 5 with section CC on FIG. 5. As angles u1 and u2 also supplement each other up to 90°, edges of rotors 1 and 2 lay in this section on minima of the deepening's of rotors 1 and 2. In position φ=45° (see FIG. 8) the section of rotors 1 and 2 coincides with section D-D on FIG. 4. Edges of rotors 1 and 2 lay in the section of minima of deepening's of rotors 5 and 6 and edges of rotors 5 and 6 lay on minima of deepening's of rotors 1 and 2.
Positions φ=90° (see FIG. 9) and φ=135° (see FIG. 10) coincide with positions φ=0° and φ=45° if to look at the drawings having turned them by 90°. The period of recurrence of a picture is 180°.
Each quarter turn of the rotors in positions φ=45°, 135°, 225°, 315° gives a spasmodic change of volume of the working chamber from V up to Vmax. At one turn of the rotors in the chamber, the value of the volume which is forced or sucked away is equal toΔV=4(Vmax−Vmin)  (4)
The attitude of ΔV to total volume of design V is equalΔV/V≈0.5  (5)
There are some major drawbacks in using this volumetric rotor machine. This design creates high pressure cavities between the internal (central cavity at end faces of rotors) and the external (outer faces of the rotors) spheres of the mechanism. The pressure zones generated create a systemic imbalance that drives fluid through the device creating a flow. As the device is configured, the gearing mechanism (the axles 7) is an integral part of the volume capture mechanism. This means that the device cannot retain pressure like other positive displacement pumps, by using seals in the contacted surfaces of the cavities. This limitation reduces the effectiveness of the design considerably as a large amount of pressure is lost through the mechanism and not imparted to the fluid in flow.
This is exacerbated by the fact that the gears 7 fill a major portion of the high pressure cavity 8. Cavity 8 is therefore not a free space cavity which would only contain fluid. Additionally, the high pressure cavity 8 is relatively small, as the radius of the inner surface 12 (see FIG. 5), is less than half the radius of the outer surface 14 of each rotor unit 1-6, restricting the volume of the now compressed fluid which can pass through the cavity 8 and out of the exhaust 9. Thus a further disadvantage of this prior art rotor mechanism is that it compresses the fluid which in turn increases the back pressure at any restrictions such as the exhaust 9.
Additionally, the device operates by being held stationary at the exhaust 9. Thus, the other five rotors can rotate about their axes 7, but the rotor containing the exhaust 9 must remain stationary as the exhaust line must be stationary. The arrangement is therefore limited to a single exhaust line. It has been found, in use, that the flow rate restrictions in the exhaust line increase back pressure through the mechanism resulting in the expulsion of fluids through the inlets which makes the entire mechanism inefficient.
The back pressure, coupled with the high pressure experienced in pulses through the mechanism also causes rapid wear and damage at the edges of the rotors.
DE19738132 to Jaitner describes a multi-element compression machine which has at least three elements rotating about fixed axles and with spiral interlocking surfaces which are out of contact to provide a minimum spacing. The elements rotate at a constant speed and generate new compression volumes which pass through the machine in a more laminar way than with conventional compression engines. No special seals are required for a high efficiency compression action.
Like Vagin, this machine also compresses the fluid which will therefore have the same disadvantages in back pressure.
U.S. Pat. No. 4,979,882 to the Wisconsin Alumni Research Foundation discloses a spherical rotary machine which may be embodied as a pump, internal combustion engine, compressor or similar other device includes an outer shell with a substantially spherical interior surface, an inner shell including a substantially spherical outer surface centered within the outer shell, and six rotary pistons located between the inner and outer shell. Each piston is rotatable about its own central axis, the six axes being orthogonally centered on the center of the machine. Each piston includes a top convex spherical surface conforming substantially in shape to and located adjacent to the spherical interior surface of the outer shell, a bottom concave spherical surface conforming substantially in shape to and located adjacent to the spherical outer surface of the inner shell, and an oval conical side surface which is substantially defined by lines which are substantially radial with respect to a point near the machine center. The oval side surface of any single piston at least nearly touches tangentially along generally radial lines the oval side surface of each of its four adjacent pistons so that any three pistons which are all adjacent to each other form a displacement chamber which varies in size as the pistons simultaneously rotate. Each piston is operably connected to a gear which is interconnected with the gears of the other pistons to regulate the relative positions of the pistons to ensure that all the pistons rotate with identical speed and direction with respect to the center of the machine. These gears may be located within or without the outer shell of the machine.
Again, like Vagin, this machine compresses the fluid and includes axles of the gearing mechanism which pass through and interrupt the high pressure cavity within the substantially spherical interior surface. In this way it has the same disadvantages as for Vagin. Additionally, there is no twist on any of the pistons, so the machine would not achieve movement of fluid from the outer surface through the exhaust as without the twist there is no means of fluid capture.
US 2006/0210419 to Searchmont LLC describes a rotary machine which can be either a pump or an internal combustion engine has a housing enclosing a plurality of rotor spindles lying on the surface of an imaginary cone for driving an output shaft positioned at the vertex of the imaginary cone. The spindles have a beveled gear on one end and engaging an output shaft and a conical bearing on the other end. Angled eccentric rotors are mounted to each spindle shaped to maintain tangential sliding contact with two adjacent rotors to form a compression or combustion chamber. A spherical version of a compressor or an engine uses a plurality of rotary pistons each of which is eccentrically mounted and forms a spherical segment. Each rotary piston is mounted for tangential sliding contact with at least two other rotary pistons to form a displacement chamber therebetween. The rotary pistons use a generally “tear drop” shape. A rotary pump has a housing having a manifold for distributing intake and exhaust air. The pump has a plurality of lobe shafts, each having an eccentrically mounted rotor attached thereto mounted in the housing to form a compression chamber in the middle of the rotor when the rotors are all in contact with each other during rotation.
Like the other prior art, this machine is designed to compress the fluid, as required of a combustion engine. The rotary pistons lack a twist angle and thus fluid capture is not achieved to move the fluid between an outer surface of the machine, to a central cavity and then via a port back to a position at the outer surface.
It is an object of the present invention to provide a rotor mechanism which obviates or mitigates at least some of the disadvantages of the prior art.